Field of the Invention
The invention relates to a method for operating an anti-theft system for a motor vehicle, and to an anti-theft system, in particular an immobilizer.
In a known anti-theft system (German Patent DE 43 08 899 C1), a three-stage dialog takes place between a key and a lock. First, the key transmits a first code signal, which is modulated into a second code signal in the lock with the aid of a computer. The second code signal is received by the key, which in turn, with the aid of an arithmetic unit, generates a third code signal that is transmitted back to the lock. In the lock, the third code signal is compared with a desired code signal, and upon correspondence a release signal is generated.
In that anti-theft system, an arithmetic unit is necessary in the key. It is only in that way that a code which changes constantly can be generated.